N = 205
a = [[0 for i in range(0, N)] for j in range(0, N)]
n = int(input())
for j in range(1, n + 1):
    if j % 2 == 0:
        a[1][j] = 2
    else:
        a[1][j] = 1
Max = 1
for i in range(2, n + 1):
    if i % 2 == 0:
        a[i][1] = 2
    else:
        a[i][1] = 1
    for j in range(2, n + 1):
        a[i][j] = a[i-1][j] + a[i][j-1]
        Max = max(Max, a[i][j])
print(Max)    